So I think the transmission in my 2001 ECSB Z71 is nearing its end. The shifts have become very sloppy and at times it will not go into gear from a stop. The truck has about 100K on it in fairly demanding traffic.

I am very interested in any advise anyone has on what to change this trans out to. In the past on other trucks I have purchased a GM CERTA rebuilt unit with good luck and they seemed to have about the same life the tranny the truck came with.

So my thought in the upgrade mode was to buy a CERTA for a 2002 Denali which would be the 4L65E and I believe it to be more heavy duty to replace my current trans. Would this work? I only want a straight swap. Are there any drawbacks? I know I could convert to the 4L80E but I just do not want all the work involved with that and really do not need that much trans for my stock truck.

In the past I spent countless hours doing research on my 4l60e that was in my z71. I finally found a simple way to prevent what kills these transmissions other than heat.
The stock filter in the transmission only filters out dirt particles down to around 100 microns. Now picture these particles acting as abrasive sandpaper getting between the valves and the valve bores in your valve body. Eventually you loose fluid apply pressure to critical components in the transmission and the trans starts slipping creating heat and reducing lube oil to critical places. overtime this loss in of fluid will take its toll on transmissions ans if you do a search for a company called Sonnax, they have very detailed technical information and very many updated parts solutions to fix the COMMON RE-OCCURRING isues that millions of people have with these transmissions. You can put a remote inline transmission filter that will filter out particles down around to 5-25 microns depending on what filter you screw on it. This will keep the fluid cleaner, and prevent premature valve body (which eventually leads to transmission failure).
If you just want a stock style trans to last you put re-man one in it or have yours rebuilt BY A VERY REPUTABLE PLACE (there are many misconceptions with the word "RE-BUILD") buy a LARGE transmission cooler, and external oil filter and change the trans fluid often It will last as long as you don't try to pull a house in overdrive or something like that.
Robby

Sun Dec 16, 2007 6:53 pm

Deputydawg

Joined: 21 Jul 2005
Posts: 360
Location: Maryland

Does anyone know if this swap is managable? I just drove my truck up to the gas station (2 miles) and on way back it shuttered and bucked 2 times hard. When I got back into my driveway the tranny was whinning real loud and would not shift out of first gear. I stopped and went to back up and there is no reverse now. Engine just revs like it is in neutral..??

Help would be greatly appreciated. She has 130k on the original trans and if it's not an easy fix I would like to replace it with something more reliable.

A 4L65-E can directly replace a 300mm TC version of the 4L60-E. (The 300mm torque converter is what's used behind all Gen-III/IV engines with the 4L60-E, these have a specific bellhousing and input shaft.)

All 4L65-E transmissions are set up with the bellhousing, TC, and input shaft for Gen-III/IV engines.

If it's a 4L65-E you want the only thing standing in your way is the cost.

Thu Dec 27, 2007 11:52 am

Deputydawg

Joined: 21 Jul 2005
Posts: 360
Location: Maryland

Thanks for the info James.

I did check on the cost and you are right. Pretty hefty. I hope that I can just fix mine and get out under $500. I saw a bunch of different rebuild kits out there for the trans. Is it hard to rebuild one if you never have before?

I would have to say it's "difficult". You have to have an infinite attention to detail and total recall for the order in which things come apart. There is a lot of agonizing and dirty work too associated with removal and reinstallation of the transmission itself - especially if four-wheel-drive.
So far I've overhauled a 4L80-E, a TH400, and a 4L60-E all of which worked right afterward. I think the most important thing is trusting your ATSG manual and taking the time to read though it without skipping any details. There are a lot of points in the process where you need to stop and measure clearances and tollerances - do it! Some things require special tools to compress the piston return springs but I've always managed to improvise or fabricate what's needed.

The most important factors for me in considering taking on a job like this are:
- How fast do I need it back on the road?
- If it does work right the first time will it mean the end of the world?
- Do I have time not to rush it?
- Time has cost. Can I afford to take the time?

Doing this overhaul yourself can save you more than $1700. That number drops fast though if you're renting a car in the mean time of if it doesn't work right on the first try and you have to start over.

Thu Dec 27, 2007 2:23 pm

MiBowHntr

Joined: 24 Jun 2008
Posts: 1
Location: Livonia, Michigan

GM Transmission

Just some input for what its worth. I have a 2005 Chevy Silverado Z71 with 91,000 miles and my trans went out. Had it overhauled at the dealer....2 days later it went out again. They overhauled it AGAIN. 1 month later it went out again. Now they want to put a GM Re-Man in it......NO WAY!!! I've been researching all the "Re-Mans" out there and look at the Jasper. They have done more than a dozen improvements to the GM Trans to prevent the very failures that have been happening. They also back it with a 100,000 mile warranty. Just look at their website and see all the improvements they have made and why......makes you wonder why GM didnt make them that way in the first place.

An automatic transmission rebuild never ever comes out better than the person's skills who did it. It takes a ridiculous amount of time to do a proper inspection and blueprinting of every part that comes out to qualify its continued servicability. There are dozens of opportunities at every step to cut corners. It comes down to the work ethics of the rebuilder sometimes.
You can tell a lot about a rebuilder by looking at their bench and their shop. It should have precision tools on it like a dial indicator, calipers, circlip pliers, specialized lip seal installers and sealing ring compressors and expanders. It should look like an operating room table, not a tool bench. There should be no clutter. There should be space for all the parts that come out and clean bins to put them into or trays to put them on to. there are a bunch of other things a shop needs to do this job right. Point is, after that many failures it's time to forbid that guy from touching your truck again - even if it means forgoing your warranty. Dealerships typically do not have many transmission techs. There will be one lead guy that usually sets up all trannies, transfer cases, and rear ends generally. The other guy fills in during absences or when they get really busy.